1. Field of the Invention
The present invention relates to a brake force detecting device for detecting a brake force produced by a disc brake.
2. Description of the Related Art
In the case of performing braking control for a vehicle, a brake force is one of the important items of information. For example, if a brake force actually applied during braking can be detected, the condition of a road surface can be easily estimated. If the condition of a road surface can be estimated, ABS control (antiskid brake system control) can be performed more precisely, and the vehicle can therefore be braked to a halt safely in a short distance. Further, if a brake force applied to each wheel can be detected in braking during turning of the vehicle or during running on a slippery road surface having a low coefficient of friction (μ), the brake forces for all the wheels can be individually controlled to thereby allow safer running control of the vehicle.
Conventionally developed is a disc brake such that a load cell is provided on a supporting and engaging portion of a support member for friction pads or a strain gauge is attached to the supporting and engaging portion to thereby detect a brake force. A brake force measuring device including a support member for measurement of a brake force as provided between a brake caliper and a knuckle arm has been proposed in Japanese Patent Laid-open No. Hei 6-123665. The brake force measuring device disclosed in this publication includes a support member interposed between a brake caliper and a knuckle arm and having a pair of substantially perpendicular beams and also includes detecting means for detecting displacement of the beams.
According to the brake force measuring device described in Japanese Patent Laid-open No. Hei 6-123665, the brake force measuring device has an H-shaped cross section, so that the distance between the caliper bracket and the knuckle in the axial direction of the brake disc is large, causing an increase in size of the measuring device. Further, it is difficult to arrange a displacement detecting device between the two beams. Further, in the brake force measuring device described in Japanese Patent Laid-open No. Hei 6-123665, deformation due to the brake force in braking during forward running of the vehicle and deformation due to the brake force in braking during reverse running of the vehicle are generated in opposite directions. Accordingly, strain is generated both in a tensile direction and in a compressive direction, so that the zero point calibration for a sensor output is difficult, causing a problem on stabilization of a detection output.